Why don't we use container ID directly

[tomatopunk]

Hi folks:

Although we can already obtain the container id by using the full container name, why isn't it exposed?

cadvisor/container/docker/factory.go

Lines 173 to 181 in 3888dda

	func ContainerNameToDockerId(name string) string {
	id := path.Base(name)
	if matches := dockerCgroupRegexp.FindStringSubmatch(id); matches != nil {
	return matches[1]
	}
	return id
	}

Why don't we use container ID directly, and instead use the container name as the label ID value in DefaultContainerLabels?

cadvisor/metrics/prometheus.go

Lines 1769 to 1784 in d91f2e6

	func DefaultContainerLabels(container *info.ContainerInfo) map[string]string {
	set := map[string]string{LabelID: container.Name}
	if len(container.Aliases) > 0 {
	set[LabelName] = container.Aliases[0]
	}
	if image := container.Spec.Image; len(image) > 0 {
	set[LabelImage] = image
	}
	for k, v := range container.Spec.Labels {
	set[ContainerLabelPrefix+k] = v
	}
	for k, v := range container.Spec.Envs {
	set[ContainerEnvPrefix+k] = v
	}
	return set
	}

The problem with this is that we cannot map back to Kubernetes information using the container ID

[SergeyKanzhelev]

is it referring to #2931? When we use cadvisor from k8s we in fact fas this problem, I sent a PR documenting it couple days back kubernetes/website#40192. I think some users depend on the current default labels format.

I understand you can build a version of cadisor that changes it: #1429

[tomatopunk]

is it referring to #2931? When we use cadvisor from k8s we in fact fas this problem, I sent a PR documenting it couple days back kubernetes/website#40192. I think some users depend on the current default labels format.

I understand you can build a version of cadisor that changes it: #1429

Actually, what I don't understand is why we need to rewrite the container name as id when outputting it.

In the container handler, we have already obtained the correct ID through regular expressions without exposing it.

https://github.com/google/cadvisor/blob/3888dda254a8fa12f1c96be24ffdc33288ea9071/container/docker/factory.go
https://github.com/google/cadvisor/blob/3888dda254a8fa12f1c96be24ffdc33288ea9071/container/containerd/factory.go

The reason why the container ID is very important is that when we call the Kubernetes API to obtain the container status of a pod, the "terminated" state only exposes the container ID.

https://github.com/kubernetes/api/blob/e3f1032953d3776ef5da09db363f00babf681791/core/v1/types.go#L2625

---

Regarding issue #1429, I believe that it cannot expose the real container ID. Here, it can only expose the configured label, and "container.id" is not a label. It should be at the same level as "container.name".

cadvisor/metrics/prometheus.go

Lines 1788 to 1812 in d91f2e6

	func BaseContainerLabels(whiteList []string) func(container *info.ContainerInfo) map[string]string {
	whiteListMap := make(map[string]struct{}, len(whiteList))
	for _, k := range whiteList {
	whiteListMap[k] = struct{}{}
	}
	return func(container *info.ContainerInfo) map[string]string {
	set := map[string]string{LabelID: container.Name}
	if len(container.Aliases) > 0 {
	set[LabelName] = container.Aliases[0]
	}
	if image := container.Spec.Image; len(image) > 0 {
	set[LabelImage] = image
	}
	for k, v := range container.Spec.Labels {
	if _, ok := whiteListMap[k]; ok {
	set[ContainerLabelPrefix+k] = v
	}
	}
	for k, v := range container.Spec.Envs {
	set[ContainerEnvPrefix+k] = v
	}
	return set
	}
	}

If possible, I can create a pull request to expose the container_id in BaseContainerLabels.